Cognitive processes and neurophysiological mechanisms of time processing in Parkinson's disease: A narrative review

Parkinson's disease (PD) is defined by the presence of motor symptoms, such as bradykinesia. However, it also involves less well-understood cognitive deficits, including impairments in time processing: the ability to perceive, estimate, and produce time intervals accurately. In this review, we summarize the existing literature on time processing in PD, with an emphasis on the different tasks used to study it, as well as on the cognitive processes and neurophysiological mechanisms contributing to time processing deficits in PD. FINDINGS: show that temporal processing deficits in PD span both motor and cognitive/perceptual domains. While dopamine replacement therapy can improve motor timing, its effects on cognitively controlled tasks-particularly those requiring attention and longer intervals-are limited. These deficits reflect dysfunction across basal ganglia, prefrontal, cerebellar, and other brain circuits, and may involve additional neurotransmitter systems such as acetylcholine, serotonin, and noradrenalin. The variety of experimental tasks used to study timing reveals the need for more precise assessments that clearly separate motor and cognitive components. Furthermore, different cognitive processes, such as explicit, implicit, sub-second, and supra-second timing as well as attention and working memory, are involved in time processing in PD. Temporal dysfunction in PD is multidimensional, resulting from a complex system of interacting neural processes. A more complete understanding of time processing in PD is needed, focusing on exploration of the non-dopaminergic aspects of time processing, and improving the design of timing tasks to better identify specific deficits and treatment targets.